This invention relates to a method of and a device for adjusting a clock by a time mark. The clock can be a digital clock or a clock indicating in quasi-analog manner with the help of a stepping motor, and that--apart from the first installation or a service--it never needs an adjustment, even after a long operational period during which a time mark is missing, and does not have a distinguishable speed- or rate deviation. The clock according to this invention works accurately under extreme interference and is power-saving.
The term "self-contained" radio-clock in this disclosure means an automatically working radio-clock which is independent of a manual adjusting process. The term "time mark" denotes a part of a modulation envelope that is transmitted by wire or wirelessly to indicate the time reference signal given by a transmitter (FIG. 9). The term radial-clock denotes a clock receiving the time mark. The term "clock radial" denotes a clock with a radio set.
The known methods of adjusting radio-clocks can be divided into three categories: 1. synchronization, 2. triggering, 3. demodulation and direct indication of a coded time information. For all these methods there are numerous variations and circuits including the necessary backup time, and a great number of publications are available. The first category includes analog or digital clocks whose internal time base is constantly or partly corrected in relation to a received reference frequency by means of automatic frequency control or phase comparison, as e.g. described by Tetzner, Karl: "Funksynchronisierte Uhren" in: Funkschau 1976, vol. 15, p. 623 (Franzis-Verlag Munchen, Federal Republic of Germany) or by Marti, Raymond: "Selbsttatige und fortlaufende Zeiteinstellvorrichtung einer Uhr" in German published patent application (Auslegeschrift) DE-AS 1,773,406. There are also applications known that derive the time base of the clock from the carrier frequency of one (or several) transmitter(s). In this case an additional change-over to a second time base is required (backup time), as described by Schreiber, Herrmann: "Steuerung einer Gebrauchsuhr durch Zeitzeichensender" in Funkschau 1977, vol. 2, p. 96 and vol. 3, p. 137 (Franzis-Verlag Munchen, Federal Republic of Germany). The second category includes digital clocks that work independently with a varying amount of accuracy and that are set at nominal value at a fixed time (mostly 0 o'clock) by means of a time mark, as e.g. described by Beck, J.: "Korrekturautomatik fur Digitaluhren" in Elektor 1974, vol. 7, p. 79 (Elektor Verlag GmbH Gangelt, Federal Republic of Germany). The third category divides into two methods: 3.1 the time code transmitter is constantly received, as e.g. described by Weiss, Reinhard: "Uhrzeit- und Normalfrequenzempfanger fur DCF 77 mit Gangreserve" in: Funkschau 1976, vol. 22, p. 964 (Franzis-Verlag Munchen, Federal Republic of Germany), 3.2 the time code transmitter only temporarily serves for adjusting the radio-clock, as e.g. described by Prof. Dr.-Ing. Hilberg, Wolfgang: "Funkuhr-Einstellung" in the published German patent application (Offenlegungsschrift) DE-OS No. 2,715,096; in this case, the switching-on of the receiver is dependent on the rate of the clock, and the exceeding of the backup time is indicated; or the method of Mukaiyama, Fumiaki, Suwa, Nagano: "Automatisches Korrekturverfahren fur eine elektronische Uhr", according to the published German patent application (Offenlegungsschrift) DE-OS No. 2,539,224, where the codedly transmitted time information serves as correction value for the digital clock at optional instants. The third category also includes receivers, e.g. television sets, that are not radio-clocks primarily but indicate the correct time after pressure on a push-button, as e.g. developed by AEG-Telefunken and described in the magazine "Elektrotechnik" vol. 6, 1972, p. 29 (Vogel-Verlag KG, Wurzburg, Federal Republic of Germany) and under the title: "Kunftig nur noch Atomzeit". Parallel to these there are various time measuring methods that define the rate of a clock by means of a transmitter signal and eliminate it by special provisions, as e.g. described by Maire, Bernard, Marin: "Elektronisches Zeitmessgerat mit automatischer Korrektur der Gangabweichung" in the published German patent application (Offenlegungsschrift) DE-OS No. 2,851,223; in this case, the rate of a clock in second steps is manually measured by means of a time mark over a long time interval, and then stored; the clock automatically corrects its stored rate within the next, same time intervals as long as a new correction invitation is signalized to the set user.
The methods mentioned have different advantages and disadvantages of which only the disadvantages to be emphasized are enumerated here: as to the 1st category: relatively long turn-on time of the receiver, which raises the susceptibility and the required energy; relatively short backup time; no self-contained operation in the original sense. As to the 2nd category: relatively inexact time indication after a longer missing time mark, because the rates of the subsequent, not corrected time intervals add up continuously; triggering is at 0 o'clock (counter reset) which makes it impossible to tune out interferences occurring regularly at that time. As to the 3rd category: a time code transmitter with a sufficient field intensity must be receivable which presupposes relatively elaborate and expensive receiving devices; the decoder circuits are relatively elaborate; the mounting of quasi-analog indicating clocks is not possible. Besides the manual operation, the aforedescribed time measuring method has the disadvantage that the rate of the clock reaches a relatively high value before correction begins.